A Morton's neuroma, or interdigital
neuroma, is a painful condition which involves a nerve on
the plantar aspect (bottom) of the foot. Occasionally
a neuroma develops following a bruising injury to the sole of the
foot, such as might be caused by jumping onto a rock or other objects,
but in general, the origin of the condition is unknown.

What is a Morton's neuroma?

The nerves located on the bottom of the foot between the metatarsal
heads (the bone of the toe closest to the foot) supply feeling,
or sensation, to the toes. One of these nerves may become irritated
by the ligament located above it, causing it to become thickened
and painful. Generally this problem occurs most often between
the third and fourth toes, but it can occur between the second and
third toes as well. It is uncommon for a neuroma to be located
between the first and second or fourth and fifth metatarsals. Rarely
is there more than one neuroma in a foot.